1. Field of the Invention
This invention relates to a magnetic disk drive which can be inserted into and removed from a slot formed in an information processing apparatus such as a note type personal computer or a portable word processor, and more particularly to a head lift mechanism for a magnetic disk drive of the type mentioned.
2. Description of the Related Art
In recent years, there has been a demand to reduce the size and increase the capacity of the magnetic disk drive, which is one type of external storage apparatus for computers. In a magnetic disk drive for a computer, a floating magnetic head is employed to prevent possible damage caused by contact thereof with a magnetic disk medium. The magnetic head of the magnetic disk drive floats keeping a small gap (0.2 to 0.3 .mu.m) above the magnetic disk, under the balance between the floating force produced by a flow of air upon high speed rotation (for example, 3,600 rpm) of the magnetic disk and the force of a spring arm which resiliently urges the magnetic head toward the magnetic disk, and reads or writes data from or onto the magnetic disk.
When rotation of the magnetic disk stops, the magnetic head is brought into contact with the magnetic disk by the spring force of the spring arm. Accordingly, when the magnetic disk is not in a rotating condition, the head may possibly adhere to the magnetic disk. Therefore, preferably, the head is normally kept out of contact with the magnetic disk when the magnetic disk is not in a rotating condition.
A conventional magnetic disk drive for a computer adopts a contact start stop (CSS) system for the relationship between the head and the magnetic disk. In the contact start stop system, while the magnetic disk is rotating, the head floats, keeping a small gap above the magnetic disk under the balance between the floating force caused by a flow of air produced by high speed rotation of the magnetic disk and the force of the spring arm which resiliently urges the head toward the disk. When rotation of the magnetic disk stops, the head is moved to a contact allowing area on the magnetic disk and is brought into contact with the magnetic disk there. While the magnetic disk remains stopped, the head and the magnetic disk remain in contact with each other.
Since the surfaces of a magnetic disk and a magnetic head are processed into mirror faces, the head may possibly adhere closely to the magnetic disk while the magnetic disk is in a stopping condition. Consequently, when the disk drive is re-started, an overload is applied to a spindle motor in order to rotate the magnetic disk, and if it tries to rotate the disk forcibly, then destruction of the head and/or damage to the surface of the magnetic disk may possibly take place. Particularly in the case where a small spindle motor with low torque is used (to reduce the size and the power consumption of the magnetic disk drive, as is the trend in recent years) if the magnetic head adheres to the disk, this makes a serious problem when the disk drive is restarted.
Recently, as propagation of small size information processing apparatus such as lap-top personal computers, note type personal computers and portable word processors proceeds, removable magnetic disk drives which can be inserted into and removed from a slot formed in such information processing apparatus have been put on the market. A slot formed in an information processing apparatus normally serves as an insertion slot for an IC card, and to this end, the dimensions of the outer profile of such a removable magnetic disk drive are designed to coincide with the dimensions of the outer profile of such an IC card.
A removable magnetic disk drive adopts a mechanism by which a spindle motor starts its rotation when the magnetic disk drive is inserted into a slot formed in an information processing apparatus, but stops its rotation when the magnetic disk drive is removed from the slot. Also such a removable magnetic disk drive has a problem in that, since it employs the CSS system for the relationship between the head and the magnetic disk, when the magnetic disk does not rotate, the head and the magnetic disk adhere to each other, resulting in failure in re-starting of the magnetic disk drive.
Further, with the removable magnetic disk drive, it sometimes occurs that, if the magnetic disk drive is removed from the slot in error while the power source is on, the magnetic disk may contact with and adhere to the disk at the position. Further, since the magnetic disk drive itself is portable, there is the possibility that the magnetic disk drive may fall inadvertently. Accordingly, there is a problem in that, when the magnetic disk drive falls, the magnetic head and the disk can be damaged by each other.